Despite age and infirmity, Fidel Castro’s hold on the American psyche remains as strong as his grip on the Cuban people. Or so it seems, considering the insistence of President Bush that virtually any economic tie between the United States and Cuba will just feed Castro’s power and the apparent unwillingness of Congress to challenge that argument.

Last week was the 45th anniversary of the Cuban missile crisis, a moment when belligerence overtook diplomacy and almost resulted in global catastrophe. The event went almost unnoticed. Instead, Bush delivered an appeal to the Cuban people — broadcast to the island from an ornate room at the State Department before an audience of Cuban dissidents — urging them to embrace U.S.-style democracy when Castro eventually succumbs.

There was little new in Bush’s speech about Cuba last week — except perhaps the promise that the United States would underwrite an effort by non-governmental organizations to bring computers to Cuba, if the government would relax its blockade of the Internet. Instead, the president rehashed four decades of economic and travel embargoes, descriptions of deprived life under Castro’s dictatorship and stories of imprisonment and terrorism.

“Cuba’s regime uses the U.S. embargo as a scapegoat for Cuba’s miseries,” the president said, before denying that the actions of the United States have added to the impoverished country’s woes and noting that his predecessors from both political parties had worked to keep Havana isolated. “As long as the regime maintains its monopoly over the political and economic life of the Cuban people, the United States will keep the embargo in place,” he insisted.

For the most part, Bush may be correct that domestic political imperatives will block any change in U.S. policy. In recent years, the House has voted on occasion to lift the ban on travel to Cuba, but the Senate has resisted. The only substantive change in U.S. law was enacted almost seven years ago and permits the sale of agricultural and medical goods to Cuba under certain limited conditions.

The result of that 2000 law is that U.S. exports to Cuba, which had been essentially zero, jumped almost overnight. Shipments of such commodities as rice, wheat, corn, soybeans, meat and poultry surged, peaking at $404 million in 2004. But then the Treasury Department stepped in and tightened the rules, making it more difficult for U.S. shippers and their Cuban buyers alike to meet the payment requirements. Exports declined each of the past two years.

There are signs, however, that trade may again be increasing, in spite of the restrictions. Through August, shipments to Cuba totaled $266 million, a 17 percent increase over the same period in 2006. And Congress is talking about relaxing the rules a bit. Provisions in the pending fiscal 2008 Financial Services appropriations bill that was passed by the House and approved in Senate committee would roll back the Treasury’s 2005 limitations on sales of food and medicine, and the Senate measure would go further to relax travel restrictions for potential shippers.

But the president has said he will veto any such bill that reaches his desk, so those who favor trade shouldn’t hold their breath.

Support for opening doors to commerce with Cuba is bipartisan and based on the same assumption that drives U.S. relations with China and Vietnam, for example: that dollars will make friends and expand the capitalist spirit, even in a communist environment. Opposition comes mostly from conservatives, yet the right is divided on this question, more so than the left.

For the Bush administration, though, a change in policy will be in order only after the Castro regime and its remnants — presumably including Fidel’s brother Ra??l, who has been acting president since July 2006 — are swept away. The question is what influence the United States might be able to exercise at that point.

The island’s infrastructure is a wreck; its agricultural base is weak and cannot feed the 11.4 million people who live there. Tourists (not from here) supply much of the foreign currency the country scrapes together to pay for roughly $10 billion in imports. The U.S.-produced share of those imports amounts to about 4 percent today. That’s not a very big lever when it comes time to move people’s minds. Instead, Cuba is likely to look to its bigger trading partners when it comes time to open its economy — a time that almost everyone thinks will come sooner or later. That means U.S. allies such as Canada, the Netherlands, Germany, Italy and Spain may have more clout than us, not to mention adversaries such as China and Venezuela, which already enjoy close ties to Cuba.

Cuba’s economy faces huge challenges, and the country needs to import capital and jobs to serve its highly educated population. Bush wants to spend almost $50 million this year to promote democracy in Cuba. The question is why he can’t imagine benefits from sending a little commerce that way, too. The embargo certainly hasn’t done much to dislodge the Castro brothers. Or does Bush really not believe in the power of capitalism after all?